When exploring for or extracting subterranean resources such as oil, gas, or geothermal energy, and in similar endeavors, it is common to form boreholes in the earth. To form such a borehole, an embodiment of which is shown in FIG. 1, a drill bit 112 may be suspended from a derrick 113 by a drill string 114. While a land-based derrick is shown, water-based structures are also common. This drill string 114 may be formed from a plurality of drill pipe sections 115 fastened together end-to-end. In other embodiments a flexible tubing may be used. As the drill bit 112 is rotated, either at the derrick 113 or by a downhole motor, it may engage and degrade a subterranean formation 116 to form a borehole 111 therethrough. Drilling fluid may be passed along the drill string 114, through each of the drill pipe sections 115, and expelled at the drill bit 112 to cool and lubricate the drill bit 112 as well as carry loose debris to a surface of the borehole 111 through an annulus surrounding the drill string 114.
At times it may be desirable to alter a direction of travel of a drill bit while it drills from a path it might naturally take through the earth. This may be to steer the drill bit toward valuable resources or away from obstacles. This may also be to merely keep the drill bit from veering off course. Either way, a variety of techniques have been developed allowing for steering of a drill bit as drilling progresses.